China is by far the most aggressive, but not the only, country attempting the sort of extensive cyberespionage described in security firm Mandiant's dramatic report, released this week.

Several other countries, most notably Russia, are involved in similar campaigns against U.S. companies from a wide range of industries, security experts said.

Companies in the information technology and communications sectors, as well as those in the marine systems, aerospace, clean technologies, healthcare, pharmaceuticals and agricultural industries have all been targets of such campaigns in recent years, they said.

"We are now in an era where global intelligence regimes within many countries are capable of extracting data and intelligence from across the world with very little effort and almost complete impunity," said Lawrence Pingree, an analyst with Gartner. "The most important aspect of these developments is that these capabilities can now be targeted and persistent at the individual actor-level with unprecedented precision."

China has attracted the most effort not only because it has been the most aggressive actor, but also because it is widely perceived as having the most to gain from such campaigns. But the fact is that other countries almost certainly have similar capabilities, Pingree said.

Mandiant on Monday released a report identifying a unit of the People's Liberation Army (PLA) of China as being behind a systematic cyberespionage campaign against the U.S. and several other countries since at least 2006. The PLA's Unit 61398, based out of a 130,663 square-foot building in Shanghai, is believed to have compromised over 140 companies from 20 major industries in countries that are considered as strategic by China, the report said.

The security firm's report provides what many believe is the best evidence yet of the extensive cyberespionage activities being directed out of China.

"[The report] goes way beyond the reports we have seen in the past that point a finger at China's cyberespionage," said Richard Stiennon, principal at IT-Harvest. "The Mandiant report establishes the extent, methodology, and scope of a single group's activity emanating from China and most probably under the direct command of a unit of the PLA.".

In releasing the report, Mandiant appears to have also burned a huge amount of critical information on major cyberthreat actors, Stiennon added. Many of the IP addresses and malware tools used to craft the attacks described in the report are likely to be abandoned by Unit 61398 in short order, Stiennon said. "It is still of extreme value to anyone who has been breached but the value for future attack detection will diminish quickly," he said.

Mandiant's report bolsters a long-held view within the U.S that entities based out of China are working on behalf of, or with the knowledge of, the Chinese government to steal U.S. intellectual property and trade secrets.

"Chinese actors are the world's most active and persistent perpetrators of economic espionage," a report by the Office of the National Counterintelligence Executive (NCIX) had noted back in October 2011. "U.S. private sector firms and cybersecurity specialists have reported an onslaught of computer network intrusions that have originated in China," the NCIX said.

The report pointed to a Chinese government initiative called Project 863, which provides funding and guidance for efforts to steal sensitive U.S. economic information and technology. "China will continue to be driven by its longstanding policy of 'catching up fast and surpassing' Western powers," it noted.

But China is not alone. Several intelligence reports, some dating back to 2005, have consistently warned about the U.S. being a target of economic espionage from state-sponsored entities around the world.

A 2012 report from the U.S. Department of Defense's Defense Security Service (DSS) says entities linked to East Asia, where China is located, and the Pacific region, accounted for 42% of all attempts to collect sensitive U.S. data illegally. The report considered a range of espionage activities, and not just cyberespionage.